Much attention has been paid in the past to the provision of an electric automobile running on electric power generated by a solar cell receiving sunrays, from the standpoint of the lack of air pollution from the exhaust gas and the saving of energy. Such an arrangement has such disadvantages, however, as inferior start-dashing, difficulty of obtaining high speeds and short travelling distance, since conventional cells are heavy and bulky, and must be mounted on the car for driving even when sunshine is not available.
Also, in computer systems, many memory devices are used, and standby power sources for emergency use must be installed so that records stored in the memory devices are not erased even upon a sudden power outage. Such power sources are heavy and bulky, requiring more area than the installation area of computer system itself, and are expensive and inconvenient to handle.